Sounds like the perfect learning curve.
Tip: negotiate the BEST price possible!

 

On these cars, a blown head gasket is typically a symptom of some other problem (for example, cooling system failure). So in addition to repairing the engine, you may need to find and fix the root cause of the problem. Something to think about.

That said, I think the B25 and B30 engines have a lot of interchangeable parts. So you could conceivably make a good working engine from the two. My suggestion would be to have the B30 head checked for warpage, and go from there. If it's warped, you can use the B30 cams in the B25 head to get your B30 back on the road. You might even get away with resurfacing the B30 head, if the warp isn't too bad.

Side Note: It seems we have similar goals. I bought a clapped-out 330i to fix up and use as a track beater (drag race / autocross). The head gasket is fine, but the timing chain guides were on the way out. They literally disintegrated on the drive home. That was exciting.

My car is also a long-term project. I've already stripped out the interior, deleted some things (A/C, SAP, windshield washer tank, etc), and did some basic modifications. I also have a build thread, if you're interested. Here's the link: Build Thread: The "Basket Case BMW" Project

 

On these cars, a blown head gasket is typically a symptom of some other problem (for example, cooling system failure). So in addition to repairing the engine, you may need to find and fix the root cause of the problem. Something to think about.

Oh yeah, I’ve done the full cooling system, intake manifold, ccv, complete suspension, ofhg, VANOS replacement, oil pan gasket, shifter rebuild, fluids, etc. on other e46s… I’ve just not had to repair physical damage to engine/driveline components yet. I would basically be stripping the car all the way down and rebuilding it new for fun.

it’s good to know that this is a feasible venture. I just wasn’t quite sure if there were any unique-to-the-b30 parts that would likely be damaged in a overheating/head gasket situation.

 

Makes perfect sense to me.
Take lots of pictures, and buy a few
decent- quality measuring tools!

t
has a barn full of stuff like that.

 

I say go for it. That's a decent price, but does not hurt to try for lower price. I bought my 02 vert for 1k with a blown motor..... broken latches, busted suspension, wrong tires....etc.

I'm now penniless, divorced and live in the trunk of the car in an abandoned rock quarry. 🤪

Kidding..... after 3 months and about 4k into it I have a solid car that my wife drives about 100 miles daily.

All I do to it now is slowly improve the interior bits.

 

Yes, this should work.

Since you don't know condition of either cylinder head, I would bring them both to a machinist and let him/her test/skim the best one...the one that needs the least work. The heads between a B25 and B30 are interchangeable, but as you know, keep cams, trays and their caps together and separate from each other.

I would suggest you time-sert the B30 block.

You should also put a straight edge and feeler gauge on the block. The M54 block does not warp as easily/frequently as a cylinder head, but you can certainly warp a block in a significant overheat.

Since this is a project, and you have the head off the B30, and presumably the engine out of the car (you don't have to I suppose, but you should pull engine so you can do the oil pan gasket), you might want to consider doing piston rings and eliminate any oil consumption issues.

 

Depending on your time frame you could just wait it out for a decent whole m54b30. Just pop it in. I've seen as low as 600 bucks for whole motors. Or look for buying a whole donor vehicle with an m54b30 in it. I paid 500 bucks for a neglected e53. The only solid thing on it is the m54b30. Purrs like a kitten.

 

This

I just rebuilt an m30 (edit: m54b30) that I bought for $300 (also zhp cams for $75)

All in about $2k for parts and $1k for tools. Could do it for less, and I have replaced the bearings and put in m52 rings. Yours will cost a little bit more because you will replace the main bearings.

A used b30 engine is closer to $1k these days, but still much cheaper.

I would do it if you have the same goal I did - to have the experience of rebuilding an engine.

On the subject of making a b25 into a b30:
1. Swap cams and cam shelves
2. Swap pistons and connecting rods
3. Swap crankshaft
4. Remember to use the b30 intake

 

Welp, she’s mine. $520 plus two catalytic converters, lol… it runs fine (with a jumpstart) until it reaches operating temp due to the head gasket situation. Tons of work to be done, but that’s what I wanted.

Hood and rear bumper are in better shape than the ones on the vert, so I’ve already gotten my money’s worth.

stupid uhaul rented my real trailer I reserved, so I had to do a no-no towing it back home.

 

Doesn't look too shabby at all. Where at in GA are you located? I can probably loan you an engine stand and lift if you are not too far from Chattanooga TN.

 

Good luck. This will be a good project.

 

Yep. B30

 

Looks like a fun project. Also looks like you already have the Style 68 wheels. That's cool.